NCP1336ADR2G 查看數據表（PDF） - ON Semiconductor

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NCP1336ADR2G

Quasi-Resonant Current Mode Controller for High Power Universal Off-Line Supplies

ON Semiconductor 

NCP1336A/B

APPLICATION INFORMATION

The NCP1336 has two operating modes: quasi resonant

operation and VCO operation.

The operating mode is fixed by the FB voltage:

• Quasi−resonant operation occurs for FB voltage higher

than 0.8 V (FB decreasing) or higher than 1.6 V (FB

increasing) which correspond to high output power and

medium output power.

During quasi−resonant operation, the operating valley

(1st, 2nd, 3rd or 4th) is fixed by the FB voltage which is

compared internally to several voltage references

corresponding to the different valleys. There is a wide

hysteresis on each valley, allowing the controller to

adjust the output power by the current−mode control

without jumping between valleys. The peak current is

variable and is set by the FB voltage divided by 4.

• VCO operation occurs for FB voltage lower than 0.8 V

(FB decreasing) or lower than 1.6 V (FB increasing).

This corresponds to low output power.

During VCO operation, the peak current is fixed to 25%

of its maximum value and the frequency is variable.

The frequency is set by the end of charge of Ct

capacitor. This capacitor is charged with a constant

current source and the capacitor voltage is compared to

an internal threshold fixed by FB voltage. When this

capacitor voltage reaches the threshold the capacitor is

rapidly discharged down to 0 V and a new period start.

Startup

NCP1336 includes a high voltage startup circuitry that

derives current from the bulk line to charge the VCC

capacitor. When the power supply is first connected to the

mains outlet, the internal current source is biased and

charges up the VCC capacitor. When the voltage on this VCC

capacitor reaches the VCCon level, the current source turns

off, reducing the amount of power being dissipated. At this

time, the controller is only supplied by the VCC capacitor,

and the auxiliary supply should take over before VCC

collapses below VCCmin. Figure 3 shows the internal

arrangement of this structure:

+

-

+

VCCon

VCCmin

HV

IC1 or IC2

VCC

GND

HV

+

Figure 3. Startup Circuitry: The Current Source Brings VCC Above 15 V and Turns Off

In some fault situations, a short−circuit can purposely

occur between VCC and GND. In high line conditions (VHV

= 370 Vdc) the current delivered by the startup device will

seriously increase the junction temperature. For instance,

since IC2 equals 3 mA (the min corresponds to the highest

TJ), the device would dissipate 370 V x 3 mA = 1.11 W. To

avoid this situation, the controller includes a novel circuitry

made of two startup levels, IC1 and IC2. At power−up, as

long as VCC is below a certain level (0.7 V typ.), the source

delivers IC1 (around 300 mA typical), then, when VCC

reaches 0.7 V, the source smoothly transitions to IC2 and

delivers its nominal value. As a result, in case of

short−circuit between VCC and GND, the power dissipation

will drop to 370 V x 300 mA = 111 mW. Figure 4 portrays

this particular behavior:

VCC

Figure 4. The Dual Level Startup Current Source

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